Telecommunications companies (Telcos) are in the process of leveraging their existing copper plants, mostly comprised of CAT3 and twisted pair, to deploy triple play services to existing customers. Digital Subscriber Lines or DSLs are ideal for existing copper plants because of their simplicity to deploy, cost, availability, and rugged performance. DSL is a medium for transferring data over regular phone lines and can be used to connect to the Internet. However, like a cable modem, a DSL circuit is much faster than a regular phone connection, even though the wires it uses are copper like a typical phone line. More and more providers, however, are offering triple play service, that is to say the bundling of two such bandwidth-intensive services as high-speed internet access and television with a less bandwidth-demanding Plain Old Telephone Service (POTS), over a single connection. In order to provide triple play service, such higher bandwidth xDSLs as Asymmetric Digital Subscriber Line (ADSL), ADSL2+, Very High Bit Rate DSL (VDSL) and VDSL2 are generally used by Telcos. The xDSL architecture, for example, connects an xDSL modem on each end of a twisted-pair telephone line, that is, at the “central office” (or node or remote terminal) and at the premises of the subscriber (the end user or customer). High and low bandwidth may be separated, or “split”, using filters or splitters at or near the end user. The term “splitter” is used to refer to a circuit or component that accomplishes this task. For example, a low pass filter or low pass and high pass filter combination separates a first signal from a combined signal in the example of a low pass filter and separates both the first and second signals from the combined signal in the example of the low pass and high pass filter combination.
The Telcos can control and monitor their existing copper plants efficiently; however, the Telcos cannot maintain or control the subscriber's copper plant after the demarcation point. This makes it difficult and expensive for the Telcos to install high speed services because of the condition of many of the subscriber copper plants after the demarcation point. Instead, the Telcos are targeting the existing coaxial infrastructure that exists in the subscriber premises.
In North America, coaxial cable, an unbalanced transmission medium, has been used a great deal since the 1970s for video transmission. A coaxial cable is a round cable where one of the conductors is a thin wire running down the middle and one conductor (usually grounded) is a cylindrical shell or braid that surrounds the first conductor. Coaxial cable has good performance through a broad frequency range, is present in a majority of American households, and can be routed passively through the subscriber premises. DSL transmission can be passively converted to coaxial cable transmission through the use of a transformer to change impedance and convert between balanced and unbalanced electrical signals. Products exist to convert between twisted pair and coaxial transmission. Such products may be too large and cumbersome for some applications, however, and may occupy from two to three positions in a standard Network Interface Device (NID).
To take advantage of the existing coaxial infrastructure, a device is needed to convert between balanced (twisted pair) and unbalanced (coaxial) electrical signals, especially a device that would occupy a single position in a NID. Additionally, an exemplary device would be suitable for use in many existing types of NIDs.